Deadly riots in the streets of Mozambique over sharply higher food prices have left 13 dead. Anger is growing in Egypt and Serbia as well. Panicked Russian shoppers have cleared the shelves of staple grains. And the devastating floods that have left as many as 10  million Pakistanis homeless are also raising concerns about the country’s ability to feed itself.

A series of isolated disasters? Not at all. The common thread: extreme weather, which is putting pressure on food supplies around the globe.